When conventional two-way valves in multi-zone, heating and cooling systems open or close, a pressure change resulting in overflow or underflow is caused. Pressure independent control valves maintain the required flow rate constant by regulating the pressure drop. The product leaflet “Pressure Independent Control Valve, Quick Selection Guide, 67-7258 PR, September 2014, Honeywell International Inc.” discloses the basic concept of such pressure independent control valves (PICV).
EP 3 059 651 A1 discloses a pressure independent control valve for controlling the flow of a liquid medium in heating and cooling systems. This pressure independent control valve comprises a valve body, a first functional group and a second functional group. The valve body provides an inlet section in which an inlet pressure of the liquid medium is present, an outlet section in which an outlet pressure of the liquid medium is present, wherein the outlet section is coaxial with the inlet section, and a middle section positioned between the inlet section and the outlet section, wherein an upstream chamber and a downstream chamber being in communication with each other through an adjustment orifice are provided with the middle section. The first functional group is defined by a control device for controlling a differential pressure between upstream of the adjustment orifice, in correspondence with the upstream chamber, and downstream of the adjustment orifice, in correspondence with the downstream chamber. The second functional group defined by an adjustment device is suitable for increasing and/or decreasing the liquid flow through the adjustment orifice.
The adjustment orifice of the pressure independent control valve disclosed by EP 3 059 651 A1 is provided by the valve body, namely by a central section of the same being inclined with respect to the inlet section and outlet section. The first functional group and the second functional group are accommodated by said inclined central section. The second functional group is a functional group tailored to a required flow rate. Flow modifications are realized by different second functional groups. This requires many extra components being produced for special purpose of usage in pressure independent control valves only.